* I bonded with my iron two pieces of viscose fabric (I used something like this heat n'bond iron on)
* then I painted with the same color I dyed my sandals, the front and the back of the fabric
* ... and let dry for one hour

THE FEATHERS:

If you click on the picture you'll get a bigger image, and you can take it as you pattern.

Be sure that the feathers are the right sizes for your sandals, tho.

Make it smaller or bigger to fit your needs.

SECOND:
* cut each pattern of the feather twice
* lay your feathers-to-be in a way that they will be mirroring each others
* draw an approximate middle line with a water soluble marker
* sew from the base of the feather up until about 1/2" to the tip
* leave the tails of the thread about 6 " long! you'll need these tails later :)

THIRD:
* align the seam in the middle of the feather on your cutting mat
* tape the tip and the bottom part of the feather on the mat
* using and x-acto knife, cut the sides of the feathers every 1/8"
and leave 1/8" before and after the seam
* lay the feathers on a surface that you can easily clean, and paint over the cuts
(the paint will seal the edges and the fabric won't fray)
{you could also use fray-check, but in some cases it leaves some marks}
* once dry, use the tails of the thread to sew at the very bottom of the straps of the sandals : two or three stitches will be more than enough - and don't forget to use a thimble... really.
* apply few drops of glue along the middle seam, place it on the straps, and sew few stitches next to the end of the seam, so that the very tip of the feather will be free.
* repeat mirroring on the other sandal.
... show around your happy feet :)